This invention relates generally to rivets, and more specifically to a spread rivet and a method for producing the same.
Rivets provide an inseparable connection of work pieces or component parts and can, where a separable connection is not required or is even undesirable, replace connection by means of bolts, washers and nuts. Ordinary rivets consist of a pin with set-head and rivet shaft. For riveting, the rivet shaft is inserted through a rivet hole stamped or drilled in advance in the parts to be joined together. The rivet is held in place on the existing set-head by means of a tool serving as a hold-on and the free end of the shaft is formed into a locking head using pressure or impact force. This type of riveting can be used only at riveting points accessible from both sides.
For connection points accessible from one side only, blind rivets are frequently used. These consist of a hollow rivet, which is penetrated from a locking head side by a rivet stud, with the rivet head on the rivet shaft of the hollow rivet and with a mandrel protruding out on the set-head side. The mandrel is joined to the rivet stud at a predetermined breaking point. For riveting, the blind rivet is inserted into the rivet hole with the locking head side first, until the set-head of the hollow rivet is in place. Then with a strong pull on the mandrel, the rivet stud is drawn into the hollow rivet so that the rivet shaft expands and is deformed to provide the locking head. The mandrel is broken off at its predetermined breaking point. The tensile force required for the riveting action can be applied only with a power tool that is often pneumatically or hydraulically driven. The waste from the ruptured mandrel and its removal is a disadvantage of this type of rivet.
These rivets are each suitable only for certain rivet holes, and the hole shape and size of the rivet shaft must be matched in order to ensure a secure union. The length of the rivet shaft must be matched to the thickness of the parts to be joined. Therefore, numerous rivet sizes and rivet forms are necessary for different uses.
Thus, there is a need in the art for a spread rivet, especially of metal, that is universally applicable and can be easily and simply seated. It should automatically adjust to different rivet hole shapes and variable fastening thicknesses of the parts to be joined.
Accordingly, the present invention is a spread rivet consisting of two parts, namely an expansion peg and a drive-in pin, which in the preassembled state of the expansion rivet are captively joined together. The expansion peg has an insertion hole in the middle that is adapted to the form of the drive-in pin, two lateral engagement wings projecting in opposite directions and two opposing spreader legs projecting downward at right angles. The drive-in pin, inserted into the insertion hole in the preinstallation, protrudes out of the expansion peg to a certain extent but is in engagement with the two spreader legs. As the drive-in pin is driven into the expansion peg, the spreader legs are spread apart by the drive-in pin.
This expansion rivet, once it has been inserted into the prepared rivet holes of two component parts to be joined together, can be seated in a simple manner and without special tools merely with a hammer blow on the drive-in pin; it is particularly employable where rivet holes are accessible from one side only. When the spreader legs are spread apart by seating of the drive-in pin, they can bend over at any level depending upon the thickness of the parts to be joined together. It can therefore adjust to rivet holes of variable size and shape and to component parts of variable thickness, so that the expansion rivet need be produced in only a few different sizes.
According to one preferential embodiment of the invention, the insertion hole (for the pin) is a longitudinal hole and the drive-in pin consists of a plate that has on one end two oppositely directed wings bent at right angles and separated from each other by a slit, and on its other end has a tip, offset by steps, which engages with the spreader legs of the expansion peg when the drive-in pin is seated in the longitudinal hole. The expansion peg and the drive-in pin are preassembled and captively joined together, whereby handling of the expansion rivet is greatly simplified.
The drive-in pin preferably has a medial reinforcement rib extending to or near the tip, and the longitudinal hole running along the expansion peg between the spreader legs is provided on both sides in its midsection, with wider portions matching the reinforcement rib. This ensures a good guide for the drive-in pin in both the preassembly and the riveting action.
Preferably, the spreader legs of the expansion peg have a strip-like form and their free ends are bent back inwardly, such that following preassembly, the steps of the drive-in pin rest on the end edges of the spreader legs.
The spreader legs can have a medial recess in their end edges, within which the steps of the drive-in pin then securely rest following the preassembly.
When shoulder tips are formed on the steps of the drive-in pin as extensions of the outer edges, inadvertent slipping of the spreader legs from the steps is prevented.
According to the preferred embodiment of the invention, the spreader legs have, near their end edges, a medial hole, that is preferably rectangular, in which the drive-in pin engages with ears formed on both sides of its triangular tip, upon preassembly. Thus, the expansion peg and the drive-in pin are captively joined together.
The spreader legs can have toothing along a side edge, which improves seating of the expansion rivet in the rivet hole of the component parts to be joined together.
Following the riveting action, i.e., following seating of the drive-in pin, the wings of the latter rest on the supporting wings of the expansion peg, and these rest on one of the component parts to be joined together. With their end edges and, respectively, the steps provided, the expanded spreader legs engage behind the ears formed at the tip of the drive-in pin and the shoulder tip formed on the steps engage in the hole in the spreader legs. In this manner, the spreader legs are held in their spread position and the joining together of the component parts is ensured.
A method according to the invention for producing such a spread rivet includes the steps of joining a strip with support wings projecting medially at right angles on both sides to the strip by a short and relatively narrow web stamped from a metal band. The method also includes the steps of stamping a longitudinal hole running in the longitudinal direction of the strip, two equally spaced round holes, and also two equally spaced, preferably rectangular, holes in the middle of the strip. The method still also includes the steps of forming the expansion peg by bending the free ends of the strip back about 180xc2x0 at the middle of the round holes, and two spreader legs by bending the strip uniformly, and at a relatively short distance from the longitudinal hole. The method further includes the steps of stamping from a metal band a key-shaped plate with two mirror-image wings on one end and separated by a slit, and on the other end a triangular tip with offset steps and ears projecting on both sides together with a short neck between the plate and its tip. The method still further includes the steps of forming the drive-in pin by bending these wings at right angles in opposite directions. The method yet further includes the steps of inserting the drive-in pin from above into the medial longitudinal hole of the expansion peg until the ears projecting laterally from the tip engage in the rectangular holes of the spreader legs of the expansion peg and the end edges of the spreader legs come into contact with the steps of the drive-in pin; and the expansion rivet is preassembled.
One advantage of the present invention is that the two parts of the expansion rivet can be simply and cost-efficiently stamped from one metal band in a single processing step and then finally formed and preassembled into the expansion rivet in a few simple bending operations.
Another advantage of the present invention is that shoulder tips extending the side edges of the plate are conveniently left on the steps, so as to engage in the rectangular holes and ensure that the spreader legs rest against the steps.
Still another advantage of the present invention is that the medial recesses stamped in the end edges of the strip further enhance engagement of the side edges with the steps.
Yet another advantage of the present invention is that reinforcement channels or reinforcement ribs formed in the strip between the longitudinal hole and the round holes enhance the stability and the strength of the finished expansion rivet, and the peripheral edges of the engagement wings of the expansion peg and the wings of the drive-in pin can be crimped.
A further advantage of the present invention is that toothing along the side edges of the strip is curved slightly upward between the longitudinal hole and the round holes, to better seat the expansion rivet in the rivet holes of the parts to be joined together.
Still a further advantage of the present invention is that a reinforcement rib running in the longitudinal direction is formed in the plate of the drive-in pin and a longitudinal hole with lateral wider portions matched to these reinforcement ribs is formed in the strip of the expansion peg, so that the drive-in pin is safely guided in both the preassembly and the riveting process.
Other features and advantages of the present invention will be readily appreciated, as the same become better understood after reading the subsequent description taken in conjunction with the accompanying drawings.